It is generally accepted that thyroid hormones, specifically, biologically active iodothyronines, are critical to normal development and to maintaining metabolic homeostasis. Thyroid hormones stimulate the metabolism of cholesterol to bile acids and enhance the lipolytic responses of fat cells to other hormones.
Thyroid hormones also affect cardiac function both directly and indirectly, e.g., by increasing the metabolic rate. For example, tachycardia, increased stroke volume, increased cardiac index, cardiac hypertrophy, decreased peripheral vascular resistance and increased pulse pressure are observed in patients with hyperthyroidism.
Disorders of the thyroid are generally treated with hormone replacement by administering either naturally occurring thyroid hormones or thyromimetic analogues thereof which mimic the effects of thyroid hormones.
Two naturally occurring thyroid hormones, namely, thyroxine or 3,5,3',5'-tetraiodo-L-thyronine (commonly referred to as "T.sub.4 ") and 3,5,3'-triiodo-L-thyronine commonly referred to as "T.sub.3 "), are shown below: ##STR2##
T.sub.3 is the more biologically active of the two and, as will be appreciated from the structural formulae provided above, differs from T.sub.4 by the absence of the 5' iodine. PA1 R.sup.1, R.sup.2 and R.sup.3 are each independently hydrogen, halogen, C.sub.1-6 alkyl, trifluoromethyl, --CN, --OCF.sub.3 or --OC.sub.1-6 alkyl; PA1 R.sup.4 is hydrogen, C.sub.1-12 alkyl optionally substituted with one to three substitutents independently selected from Group Z, C.sub.2-12 alkenyl, halogen, --CN, aryl, heteroaryl, C.sub.3-10 cycloalkyl, heterocycloalkyl, --S(O).sub.2 NR.sup.9 R.sup.10, --C(O)NR.sup.9 R.sup.10, --(C.sub.1-6 alkyl)-NR.sup.9 R.sup.10, --NR.sup.9 C(O)R.sup.10, --NR.sup.9 C(O)NR.sup.9 R.sup.10, --NR.sup.9 S(O).sub.2 R.sup.10, --(C.sub.1-6 alkyl)-OR.sup.11, --OR.sup.11 or --S(O).sub.a R.sup.12, provided that, where R.sup.5 is not fluoro, R.sup.4 is --S(O).sub.2 NR.sup.9 R.sup.10, --C(O)NR.sup.9 R.sup.10, --(C.sub.1-6 alkyl)-NR.sup.9 R.sup.10, --NR.sup.9 C(O)R.sup.10, --NR.sup.9 C(O)NR.sup.9 R.sup.10, --NR.sup.9 S(O).sub.2 R.sup.10, --(C.sub.1-6 alkyl)-OR.sup.11, --OR.sup.11 or --S(O).sub.a R.sup.12 ; PA1 or R.sup.3 and R.sup.4 may be taken together to form a carbocyclic ring A of the formula --(CH.sub.2).sub.b -- or a heterocyclic ring A selected from the group consisting of --Q--(CH.sub.2).sub.c -- and --(CH.sub.2).sub.j --Q--(CH.sub.2).sub.k -- wherein Q is O, S or NR.sup.17, wherein said carbocyclic ring A and said heterocyclic ring A are each independently optionally substituted with one or more substituents independently selected from C.sub.1-4 alkyl, halide or oxo; PA1 R.sup.5 is fluoro, hydroxy, C.sub.1-4 alkoxy or OC(O)R.sup.9 ; PA1 or R.sup.4 and R.sup.5 may be taken together to form a heterocyclic ring B selected from the group consisting of --CR.sup.9.dbd.CR.sup.10 --NH--, --N.dbd.CR.sup.9 --NH--, --CR.sup.9.dbd.CH--O-- and --CR.sup.9.dbd.CH--S--; PA1 R.sup.6 is hydrogen, halogen, C.sub.1-4 alkyl or trifluoromethyl; PA1 R.sup.7 is hydrogen or C.sub.1-6 alkyl; PA1 R.sup.8 is --OR.sup.9 or --NR.sup.19 R.sup.20 ; PA1 R.sup.9 and R.sup.10 for each occurrence are independently (A) hydrogen, (B) C.sub.1-12 alkyl optionally substituted with one or more substituents independently selected from Group V, (C) C.sub.2-12 alkenyl, (D) C.sub.3-10 cycloalkyl optionally substituted with one or more substituents independently selected from C.sub.1-6 alkyl, C.sub.2-5 alkynyl, C.sub.3-10 cycloalkyl, --CN, --NR.sup.13 R.sup.14, oxo, --OR.sup.18, --COOR.sup.18 or aryl optionally substituted with X and Y, (E) aryl optionally substituted with X and Y, or (F) het optionally substituted with X and Y; PA1 or R.sup.9 and R.sup.10 for any occurrence may be taken together to form a heterocyclic ring C optionally further containing a second heterogroup selected from the group consisting of --O--, --NR.sup.13 -- and --S--, and optionally further substituted with one or more substituents independently selected from C.sub.1-5 alkyl, oxo, --NR.sup.13 R.sup.14, --OR.sup.18, --C(O).sub.2 R.sup.18, --CN, --C(O)R.sup.9, aryl optionally substituted with X and Y, het optionally substituted with X and Y, C.sub.5-6 spirocycloalkyl, and a carbocyclic ring B selected from the group consisting of 5-, 6-, 7- and 8-membered partially and fully saturated, and unsaturated carbocyclic rings, and including any bicyclic group in which said carbocyclic ring B is fused to a carbocyclic ring C selected from the group consisting of 5-, 6-, 7-and 8-membered partially and fully saturated, and unsaturated carbocyclic rings; PA1 R.sup.11 is C.sub.1-12 alkyl optionally substituted with one or more substituents independently selected from Group V, C.sub.2-12 alkenyl, C.sub.3-10 cycloalkyl, trifluoromethyl, difluoromethyl, monofluoromethyl, aryl optionally substituted with X and Y, het optionally substituted with X and Y, --C(O)NR.sup.9 R.sup.10 or --C(O)R.sup.9 ; PA1 R.sup.12 is C.sub.1-12 alkyl optionally substituted with one or more substituents independently selected from Group V, C.sub.2-12 alkenyl, C.sub.3-10 cycloalkyl, aryl optionally substituted with X and Y, or het optionally substituted with X and Y; PA1 R.sup.13 and R.sup.14 for each occurrence are independently hydrogen, C.sub.1-6 alkyl, C.sub.2-6 alkenyl, --(C.sub.1-6 alkyl)-C.sub.1-6 alkoxy, aryl optionally substituted with X and Y, het optionally substituted with X and Y, --(C.sub.1-4 alkyl)-aryl optionally substituted with X and Y, --(C.sub.1-4 alkyl)-heterocycle optionally substituted with X and Y, --(C.sub.1-4 alkyl)-hydroxy, --(C.sub.1-4 alkyl)-halo, --(C.sub.1-4 alkyl)-poly-halo, --(C.sub.1-4 alkyl)-CONR.sup.15 R.sup.16 or C.sub.3-10 cycloalkyl; PA1 R.sup.17 is hydrogen, C.sub.1-6 alkyl, --COR.sup.9 or --SO.sub.2 R.sup.9 ; PA1 R.sup.18 is hydrogen, C.sub.1-6 alkyl, C.sub.2-6 alkenyl, --(C.sub.1-6 alkyl)-C.sub.1-6 alkoxy, aryl optionally substituted with X and Y, het optionally substituted with X and Y, --(C.sub.1-4 alkyl)-aryl optionally substituted with X and Y, --(C.sub.1-4 alkyl)-heterocycle optionally substituted with X and Y, --(C.sub.1-4 alkyl)-hydroxy, --(C.sub.1-4 alkyl)-halo, --(C.sub.1-4 alkyl)-poly-halo, --(C.sub.1-4 alkyl)-CONR.sup.15 R.sup.16, --(C.sub.1-4 alkyl)-(C.sub.1-4 alkoxy) or C.sub.3-10 cycloalkyl; PA1 R.sup.19 is hydrogen or C.sub.1-6 alkyl; PA1 R.sup.20 is hydrogen or C.sub.1-6 alkyl; PA1 W is O, S(O).sub.d, CH.sub.2 or NR.sup.9 ; PA1 Group Z is C.sub.2-6 alkenyl, C.sub.2-6 alkynyl, halogen, --CF.sub.3, --OCF.sub.3, hydroxy, oxo, --CN, aryl, heteroaryl, C.sub.3-10 cycloalkyl, hetercycloalkyl, --S(O).sub.a R.sup.12, --S(O).sub.2 NR.sup.9 R.sup.10, --C(O)R.sup.9 R.sup.10, and --NR.sup.9 R.sup.10 ; PA1 Group V is halogen, --NR.sup.13 R.sup.14, --OCF.sub.3, --OR.sup.9, oxo, trifluoromethyl, --CN, C.sub.3-10 cycloalkyl, aryl optionally substituted with X and Y, and het optionally substituted with X and Y; PA1 het for each occurrence is a heterocyclic ring D selected from the group consisting of 4-, 5-, 6-, 7- and 8-membered partially and fully saturated, and unsaturated, heterocyclic rings containing from one to four heteroatoms independently selected from the group consisting of N, O and S, and including any bicyclic group in which said heterocyclic ring D is fused to a benzene ring or a heterocyclic ring E selected from the group consisting of 4-, 5-, 6-, 7- and 8-membered partially and fully saturated, and unsaturated, heterocyclic rings containing from one to four heteroatoms independently selected from the group consisting of N, O and S; PA1 X and Y for each occurrence are independently (A) hydrogen, (B) halogen, (C) trifluoromethyl, (D) --OCF.sub.3, (E) --CN, (F) C.sub.1-6 alkyl optionally substituted with one or more substituents independently selected from the group consisting of halogen, --OCF.sub.3, --CF.sub.3 and phenyl, (G) C.sub.1-6 alkoxy, (H) aryl optionally substituted with one or more substituents independently selected from the group consisting of halogen, --OCF.sub.3, --CF.sub.3, C.sub.1-4 alkyl and C.sub.1-4 alkoxy, (I) --C(O).sub.2 R.sup.13, (J) --C(O)NR.sup.13 R.sup.14, (K) --C(O)R.sup.13, (L) --NR.sup.13 C(O)NR.sup.13 R.sup.14 and (M) --NR.sup.13 C(O)R.sup.14 ; or X and Y for any occurrence in the same variable may be taken together to form (a) a carbocyclic ring D of the formula --(CH.sub.2).sub.e -- or (b) a heterocyclic ring F selected from the group consisting of --O(CH.sub.2).sub.f O--, (CH.sub.2).sub.g NH-- and --CH.dbd.CHNH--; PA1 a and d are each independently 0, 1 or 2; PA1 b is 3, 4, 5, 6 or 7; PA1 c, f, g, j and k are each independently 2, 3, 4, 5 or 6; and PA1 e is 3, 4, 5, 6 or 7. PA1 R.sup.6 is hydrogen, R.sup.7 is hydrogen, R.sup.8 is ethoxy, hydroxy or NH.sub.2, and R.sup.10 is hydrogen or methyl. PA1 coupling a 4-nitrophenol (or a corresponding thiophenol) 2 with a bis-aryl iodonium tetrafluoroborate 3 at about RT in a suitable organic solvent such as, for example, dichloromethane, chloroform, DMF or DMSO, in the presence of a suitable copper catalyst such as, for example, copper bronze and a suitable base such as, for example, TEA, potassium-t-butoxide or sodium hydride (J. Med. Chem, 38: 695-707 (1995)); ##STR10##
T.sub.3 may be produced directly from the thyroid gland, or, in peripheral tissues, by the removal of the 5' iodine by deiodinase enzymes. Thyromimetic analogs are often designed to be structurally similar to T.sub.3. In addition, naturally occurring metabolites of T.sub.3 are known.
As discussed above, thyroid hormones affect cardiac functioning, for example, by causing an increase in the heart rate and, accordingly, an increase in oxygen consumption. While the increase in oxygen consumption may result in certain desired metabolic effects, nonetheless, it does place an extra burden on the heart, which in some situations, may give rise to damaging side effects. Therefore, as is known in the art, such as described by A. H. Underwood et al. in an article published in Nature, Vol. 324: pp. 425-429 (1986), efforts have been made to synthesize thyroid hormone analogs which function to lower lipids and serum cholesterol without generating the adverse cardiac effects referred to above.
U.S. Pat. Nos. 4,766,121; 4,826,876; 4,910,305; and 5,061,798 disclose certain thyroid hormone mimetics, namely, 3,5-dibromo-3'-[6-oxo-3(1H)-pyridazinylmethyl]-thyronines.
U.S. Pat. No. 5,284,971 discloses certain thyromimetic cholesterol lowering agents, namely, 4-(3-cyclohexyl4-hydroxy or -methoxy phenylsulfonyl)-3,5 dibromo-phenylacetic compounds.
U.S. Pat. Nos. 5,401,772; 5,654,468; and 5,569,674 disclose certain lipid lowering agents, namely, heteroacetic acid derivatives, which compete with radiolabeled T.sub.3 in binding assays using rat liver nuclei and plasma membrane preparations.
Certain oxamic acids and derivatives thereof are known in the art, e.g., U.S. Pat. No. 4,069,343 describes the use of certain oxamic acids to prevent immediate type hypersensitivity reactions; U.S. Pat. No. 4,554,290 describes the use of certain oxamic acids to control pests on animals and plants; U.S. Pat. No. 5,401,772 discloses certain oxamic acids as lipid lowering agents; U.S. Pat. No. 5,232,947 describes the use of certain oxamic acids to improve damaged cerebral functions of the brain; and European Patent Specification published as EP 580,550 discloses certain oxamic acid derivatives as hypocholesteremic agents.
In addition, certain oxamic acid derivatives of thyroid hormones are known in the art. For example, N. Yokoyama et al. in an article published in the Journal of Medicinal Chemistry, 38 (4): 695-707 (1995) describe replacing a --CH.sub.2 group in a naturally occurring metabolite of T.sub.3 with an --NH group resulting in --HNCOCO.sub.2 H. Likewise, R. E. Steele et al. in an article published in International Congressional Service (Atherosclerosis X) 1066: 321-324 (1995) and Z. F. Stephan et al. in an article published in Atherosclerosis, 126: 53-363 (1996), describe certain oxamic acid derivatives useful as lipid-lowering thyromimetic agents yet devoid of undesirable cardiac activities.
All of the documents cited herein, including the foregoing, are incorporated by reference herein in their entireties.